A cryogenic engine for a space apparatus is provided. The cryogenic engine includes an injector body, a thrust chamber, and a spark plug, where the injector body is provided therein with an accommodating space; the spark plug is provided on one side of the injector body, and an electrode provided on the spark plug extends into the accommodating space; the thrust chamber is provided on the other side of the injector body and is communicated with the accommodating space; the injector body is provided with a combustion improver flow channel and a combustible agent flow channel; and the combustion improver flow channel and combustible agent flow channel are connected with the accommodating space.